I'd still recommend chewing gum, but you'd have to weigh the evidence for yourself, cause I'm not a doctor. However I believe the oral health benefits outweigh the potential risks. Acid reflux is also correlated with a lot of really nasty health issues, like esophageal cancer and heart disease. (It's my understanding that the heart disease link may be due to the elevated calcium levels caused by consuming large quantities of antacids) If chewing gum helps control your acid reflux I'd keep chewing gum. I'm actually considering this myself now that you mention it, since I suffer from acid reflux as well.

Chewing gum greatly reduces the amount of antacids I need to consume. The other thing that really surprised me was my low-carb diet further reduced antacid use to almost zero. For a month after my low-carb diet, I didn't even think to take a single antacid.

On a somewhat related note, my non-expert opinion is that sugarless gum is probably still better for you than gum with actual sugar in it for reasons relating to oral heath.